Hi i have a macbook pro and ps3 media server. the media server works perfect to stream music to my ps3 when i'm controlling my ps3. But i would also like to use it like you would use mac airplay. So play songs on my macbook and listen to them using my ps3 and sound system attached to it.

Yes...just tried it and from my MacBook (10.6.8) and using PMS 1.50 (B2) I was able to stream music from my iTunes library on the MacBook and then into my Sony receiver in the my Media Room where my PS3 is. You are probably aware, the best way (in my opinion) is to use an Airport Express next to your receiver/sound system and use the Airplay icon from your MacBook/iTunes directly or even an iPhone/Music to play music/radio stations.

Yes, without an Airport Express go to PS3 Media Server and look for 'Navigation/Share Settings', I checked 'Show iTunes Library' and 'Show iPhoto Library', 'Save' and 'Restart HTTP server'. You then go to your PS3 and you should look for 'iTunes/iPhoto Library' and play your selection. Good luck!